Mr. Rand said that Johnson Toribiong, the country’s president, would announce the ban in a speech on Friday at the United Nations. Conservation experts with Pew, a nonprofit organization based in Washington, have been working with Palau on the ban, which they describe as a first.

It will apply to waters covering an area about the size of Texas that are home to scores of shark species, Mr. Rand said.

Mr. Rand conceded that Palau, which has a population of barely 20,000, would have difficulty enforcing the ban, but he said the country was a leader in marine conservation and added that he expected other countries would follow Palau’s lead on the issue.